Various methods have been proposed for the purpose of separating methane and nitrogen.
For example, there has been proposal of a means for adsorption and removal of nitrogen by use of a pressure swing adsorption method using a molecular sieve of activated carbon (reference is made to Patent Literature 1), or a method of adsorption and removal of nitrogen by a pressure swing adsorption method using ETS-4 in which cations are exchanged to barium (reference is made to Patent Literature 2).
Furthermore a means for separating nitrogen by a membrane separation method respectively using a CHA-type zeolite membrane, a DDR type zeolite membrane or an organic membrane is also known (reference is made to Non-Patent Literature 1 to 3).